1. Field of the Invention
The invention generally relates to a device that allows for a conformal radiation dose distribution by allowing medical personnel to change the position and angle of a radiation source by inflating two balloons, whereby an inner-balloon positions treatment catheters within an outer-balloon.
2. Description of Related Art
In diagnosing and treating malignant tumors, medical physicians all over the world have tried to create innovative devices designed to treat cancerous tumors. At one time cancer could only be diagnosed when a tumor was big enough to see or feel. Now sophisticated imaging systems can identify tumors far earlier, often before any symptoms have even appeared, thereby allowing for early treatment and potential cure. Over the years many different methods have been developed to treat cancer. For breast cancer, surgical approaches such as radical mastectomies were used to remove the breast, chest muscles and underarm lymph nodes. These procedures were occasionally performed as early as the 19th century. The late 1940s brought the modified radical mastectomy, which spared the muscle tissue of the patient. In the 1970s, a more limited surgical option came into use, known as Breast Conservation Surgery, which focused on removal of the tumor and a small amount of surrounding tissue commonly referred to as a lumpectomy. In 1985, the lumpectomy combined with whole breast radiation therapy was found to be as effective as the mastectomy in terms of survival rates, but resulted in higher local relapse rates. As a result, medical research looked to provide other forms of combined surgical and localized radiation treatment options.
Beginning in the 20th century, shortly after radiation began to be used for diagnosis and therapy, it was discovered that radiation could cause cancer as well as cure it. Many early radiologists used the skin of their arms to test the strength of radiation from their radiotherapy machines. These radiologists looked for a dose that would produce a pink reaction, referred to as an erythema, which looked like sunburn. They called this the “erythema dose,” and this was considered an estimate of the proper daily fraction of radiation. In retrospect, it is no surprise that many developed leukemia.
Today, a lumpectomy is a common surgical procedure designed to remove a discrete lump, usually a benign or malignant tumor from an affected woman's breast, or in rare occasions, a man's breast. As the tissue removed is generally quite limited and the procedure relatively non-invasive, compared to a mastectomy, a lumpectomy is considered a viable means of “breast conservation” or “breast preservation” surgery with all the attendant physical and emotional advantages of such an approach.
In the past, a few breast balloon brachytherapy devices have been developed. The most common types available are the Contura® multi-lumen balloon breast brachytherapy device, and the MammoSite® breast brachytherapy device. Both devices are used in a procedure known as Accelerated Partial Breast Irradiation. These devices can have certain drawbacks which will be described in detail below.
An example of a brachytherapy applicator is the “MammoSite® Radiation Therapy System (RTS),” developed by Proxima Therapeutics, Inc., Alpharetta, Ga. 30005 USA. The MammoSite® RTS, a balloon catheter which is used in a high dose rate radiation procedure, was introduced specially for use in partial breast irradiation. The MammoSite® catheter is inserted at the time of a lumpectomy or within 30 days following surgery, remains in place during treatment, and is deflated and removed at the end of treatment, typically with a patient receiving a mild pain medication. A solid radiation source is typically used. However, a liquid radiation source can also be used with a balloon device placed within a body cavity, such as exhibited in Iotrex®, by Proxima Therapeutics, Inc. The solid radiation source can be removed following each treatment session, while the liquid radiation source typically remains in place as long as the balloon remains within the body cavity.
Clinical trials have shown the efficacy of inflatable treatment delivery devices and systems, such as the MammoSite® RTS and similar devices and systems. For example, such systems can include systems offered by GliaSite® RTS and Proxima Therapeutics, Inc. However, radiation treatment delivered via these devices and systems can have an effect on healthy tissue, while providing a desired effect on cancerous tissue, and, as such, can have a limited dose optimization, and can be attributed to their design. In a radiation treatment, care must be taken to direct the maximum therapeutic dose to diseased tissue while minimizing radiation dose to healthy tissue. For example, radiation treatment can be relatively most effective when substantially all surrounding tissue regions receive the same dose of radiation, and where the radiation dosage received by more distant tissue is as small and as uniform as possible. However, because tissue cavities typically are not uniform in their sizes or shapes and can be near critical structures, such as the skin, a lung, or the heart, radiation delivered via the aforementioned inflatable delivery devices can result in less than optimal dosages to different regions of surrounding tissue in that the treatment catheters of such known inflatable delivery devices are substantially limited in movement or are fixed in the device and, therefore, are fixed in the cavity. This can create regions referred to as “hot spots” and can also create regions of relatively low dosage referred to as “cold spots.”
In addressing non-uniform cavities as can be present in a treatment of the surrounding tissue, various devices and systems have been developed to draw adjacent tissue near a treatment device. See, for example, U.S. Pat. No. 6,923,754 B2 to Lubock and U.S. Pat. No. 6,955,641 B2 to Lubock. The Lubock patents describe devices and systems that utilize a vacuum to draw tissue surrounding a body cavity towards a treatment device placed within the cavity. The Lubock devices add a sheath or a fluid-permeable enclosure wall and a vacuum conduit to the MammoSite® RTS or similar inflatable treatment delivery device. These added elements create suction around the device, which draws tissue against the device surface within a body cavity, as can allow a closer contact between the tissue and the device. Control over the distance, spacing, and the amount of tissue contact can offer some advantages to the treatment of a lining of a body cavity.
However, with such devices and systems, a relatively common shortcoming of these applicators is that the source typically can only travel in or near a central catheter or a centralized set of catheters within a cylindrical or spherical balloon applicator. Typically, the existing balloon catheters only allow an offset from the center shaft of approximately 0 mm to 5 mm, for example. Such designs can limit the ability to maximize dose conformality and homogeneity, which can only be maximized by allowing the treatment catheters to be placed significantly farther away from the central position. For example, after a surgery, doctors may find that the cavity wall is near sensitive regions which may have a higher sensitivity to radiation damage, including development of new cancerous tissue, than other areas surrounding the resection cavity. Doctors typically are always looking to deliver the maximum prescribed dose to the target region while minimizing dose to critical structures. Therefore, there is a need in the art to move the treatment catheters farther away from the central shaft of the balloon device to provide enhanced dose conformality, or dose shaping. This can allow for greater flexibility in dose delivery to both target structures, as well as those regions where reduced dose would be beneficial.
Design of intra-cavity applicators for brachytherapy can be a challenging process, as the bio-mechanical and radiation dosimetry properties of the applicators should desirably minimize the trauma to the patient during the applicator insertion process. Further, these applicators desirably should allow optimal radiation dose conformality to the tumor tissues. Finally, these applicators desirably should have adequate mechanical strength so that the location of the applicator can be predicted throughout a course of treatment. Developments in medical imaging, such as computerized axial tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) imaging, have provided clinicians with various means to identify tumors on patient images at earlier stages with relatively increased confidence. However, as described, technical mechanisms to deliver an enhanced conformal dose can be limited by the available applicators. Therefore, it would be desirable to provide devices and systems for treatment that promote achieving an optimal radiation dose distribution to a variety of tumors in or near body cavities.
Thus, apparatuses and methods for addressing the aforementioned problems are desired.